Organic sulfur mineralization in surface soils from coastal wetlands with different flooding periods affected by the flow-sediment regulation in the Yellow River Delta, China

Abstract

Soil organic sulfur mineralization can provide absorbable sulfate for plants. However, little is known about the influencing mechanisms of hydrological conditions on soil organic sulfur mineralization in coastal wetlands. Here, an in-situ incubation experiment was conducted to identify the seasonal characteristics of organic sulfur mineralization rates (RNSM) from April to October in surface soils in the seasonal flooding wetlands (SEW), the short-term flooding wetlands (SHW) and the tidal flooding wetlands (TIW) affected by flow-sediment regulation. The results showed lower electrical conductivity (EC) and sand contents and higher water content, and silt and clay contents in SEW, SHW and TIW soils after flow-sediment regulation. The dehydrogenase enzyme activity values in three wetland soils increased from May to August and then decreased after August. Generally, the microbial biomass carbon levels in three wetland soils decreased firstly from May to June and then increased from June to September. However, both arylsulfatase enzyme activity and microbial biomass nitrogen showed different seasonal fluctuations in three wetland soils. The RNSM values in three wetland soils were obviously enhanced during the regulation, but higher RNSM values were observed in SEW soils. Soil properties such as EC and microbial activity were the main factors influencing the RNSM values in these wetland soils. These findings of this study can provide an in-deep understanding of organic sulfur mineralization in wetland soils of the ecotone formed by the interaction between freshwater and seawater in the large river deltas.